Steam baking oven



Jan. 18, 1938. w. PFEIFFER STEAM BAKING OVEN Filed Sept, 22, 1 936 J/ A gr.

0 O ma Patented Jan. 18, 1938 UNITED STTES STEAM BAKING OVEN Wilhelm Pfeiffer, Tepl, near Karlsbad, Czechoslovakia Application September 22, 1936, Serial No. 101,996 In Austria July 2'7, 1935 4 Claims.

Steam baking ovens are known in which the heating tubes are connected with a steam generator to form a pressure-proof heating circuit. The forms of construction hitherto employed are however not suitable for economical operation. Moreover the generation of steam cannot be effected in a simple manner without the risk of explosion.

The object of the present invention is to obviate these defects and to provide the advantage of the simplest and 'most reliable construction by employing, for the generation of steam, pipe coils of which the beginning and end are connected through a steam separator which separates the steam from the water. The steam flows away to therheating bodies, and the water flows back again to the lowest ends of the pipe coils. This renders possible a rapid circulation of water and at the same time an undisturbed generation of steam. Furthermore the Vaporizers are so selected and arranged that the Volume thereof is very small in comparison with the total volume of the heating circuit, and the water filling thereof is made less than three-tenths of a kilogram of water to each liter of the volume of the heating circuit, so that the critical condition of the water vapour cannot be reached even in the event of accidental or malicious overheating, whereby the greatest danger of an explosion is eliminated.

The arrangement of the coil tubes may be different, and the steam generator may be formed of any number of such tubes. The arrangement of the separator may also be different. It may consist of a more or less inclined piece of tubing,

35 into the higher portions of which the upper ends of the coil tubes open, and the lower portion of which is connected with the lower ends of the coil tubes. The separator may alternatively consist of an upright length of tubing. With a plurality 40 of coil tubes there may be employed a horizontal tube,'into which the ends of the coil tubes open, radially or otherwise.

From thehighest point of the separator the steam is led to the heating units, and from the lowest point the water is returned to the lower ends of the coil tubes.

Alternatively the header or collecting tube of the heating units of the baking chamber may be constructed as a steam separator. In particular an arrangement of the heating units in which the heating tubes open into a common header or collecting tube is suitable for this purpose.

For baking ovens of small or medium size an arrangement of the steam generator is advantageous in which the coil tubes form one or more where the furnace gases are of a high temperature, radiation unitsof fire-proof material, which become incandescent and furnish radiant heat to the steam generator. At the same time the radiating bodies are so arranged that the furnace gases are mixed, as a result of which the gases are completely burnt.

A further object of the invention is to provide, in the condensate return from the baking chamber heating units to the steam generator, a constriction or a non-return valve, so that a high 1 static pressure of the condensate is obtained. This obviates the risk, particularly when heating up the baking oven, that is, when the steam pressure is low and its volume great, of the steam passing into the condensate return tube in the event of a transient impulsive generation of steam, thereby obviating obstructions in the condensate return.

Further details of the invention will be gathered from the accompanying drawing, which i1- lustrates various embodiments of the invention.

Figure 1 shows a baking oven according to the invention in sectional elevation;

Figure 2 shows a sectional plan through a baking oven;

Figure 3'shows in sectional elevation a steam generator and heating circuit;

Figure 4 is a plan view of the steam generator, and l Figure 5 shows an auxiliary low pressure steam generator in sectional elevation.

In Figures 1 and 2, heating tubes 1 open into a common header or collecting tube 2. The upper ends of pipe coils 3 and 4 open into a steam separator 5, in which the steam is separated from the water. The steam flows by way of a pipe 8 tothe collecting tubes 2. The water flows back from the separator 5 through a pipe 6 into the lower ends of the pipe coils 3 ands. The steam from the collecting tubes 2 flows into the heating tubes l, which exhibit a certain amount of drop in relation to the connecting tubes 2, so that the condensate formed flows back to the latter. From here it passes by way of a pipe 9 and a non-return valve H], which may be a ball valve, back to the steam generator. In the interior of the pipe coil 3 there is a radiation body I 2, with plates l3. Owing to the furnace gases from the fire located underneath, these plates i3 become incandescent, and the radiation body 52 gives up its heat to the pipe coils 3. By the plates I3 unburnt gases and air are mixed and become completely burnt. The furnace gases heat the further heating surfaces of the pipecoils 3 and 4, and heating ribs H provided on the latter, and then pass to the chimney. In carriers l5 holes are provided, through which the heating tubes pass, for the purpose of securing the heating bodies in the baking chamber. The carriers l5 serve at the same time for supporting the baking hearth or the cover of the baking chamber.

In Figures 3 and 4 a pipe coil 39 is embedded in metal, cast iron for example, and the latter is provided with heating ribs 40 and H, for the pur pose of providing a large heating area with a minimum volume of the vaporizing pipes, and also for the purpose of armouring the pipe coil and protecting it against overheating. The upper end of the pipe coil 33 is connected by a pipe 3| with the lower collecting tube or header 32. The lower end of the pipe coil 30 is connected by a pipe 33 with the other end of the collecting tube 32. The mixture of steam and Water formed in the pipe coil 38 ascends in the pipe 3| and enters the collecting tube 32. The steam separated here passes into the heating tubes 36, and also through the pipe 34 into the upper collecting tube 35, and from here into the heating tube 36. The condensate formed here flows back into the collecting tube 35, and passes from here through the pipe 31 into the lower collecting tube. From the latter the condensate and the separated water flow back through the pipe 33 to the steam generator, that is, to the lower end of the pipe coil 30.

38 is a radiation body with plates 39, for the utilization of the radiant heat and for the complete combustion of the furnace gases from the fire located underneath. In the present case a special separator is not required, but the collecting tube of the heating body is constructed as a separator. The steam separator may be arranged in a different manner from that illustrated in Figures 1 and 2, and in particular it may be located higher than is shown there. For instance it may even be located higher than the collecting tubes 2, for the purpose of obtaining a greater up-rush of the mixture of water and steam and a more rapid circulation.

Figure 5 shows in sectional elevation an auxiliary generator heated from the heating circuit of the baking oven for the production of steam for the baking chamber. The heating thereof is effected by a pipe coil 5B, which is cast in a heating body 53, by means of steam from the heating circuit of the baking oven. The steam pipe 5! is connected for example to the steam pipe 8 of Figure 1, and the condensate pipe 52 to the. pipe 9 of Figure l. The cylindrical external periphery of the heating body 53 is turned smooth and somewhat conical, the upper end being of smaller diameter than the lower end. A hood 54 has spiral projections 56, which are mounted fast upon the heating body 53 internally, so that the transmission of heat is good. Tie hood 54 is secured to the heating body with screws. The water to be evaporated is admitted at 51, and flows downwards on to the spiral projections 55, being then vaporized. These projections 56 have rough or ridged surfaces, so that the water has to flow down slowly. The steam formed flows upwards into the spiral space between the projections 55, and passes through a pipe 58 into the baking chamber. By this device the steam necessary for the baking chamber can be generated very quickly and continuously, because the transmission of heat from the heating fluid (steam at a pressure of from 50 to 80 atmospheres) from the heating circuit of the baking oven to the vaporizing surfaces proceeds of itself very intensively. The small weight of the closed generator is therefore suificient as compared with the great weight of the means hitherto employed.

In this connection it is to be noted that the devices does not relate to means for the generation of steam for heating the oven but to means for generating steam which is blown into the oven from time to time and which is effective to improve the quality of the ware. Hitherto heavy iron plates have been employed which were placed underneath the oven from which it was heated by the radiant heat of the plates and the steam introduced into the oven being produced by pouring water from time to time over the iron plates.

According to the present invention the steam generator for introducing steam into the baking oven is heated by the heating circuit of the oven. This arrangement has the following advantages:

1. The heat from the heating circuit is quickly and economically transmitted to the steam generator due to the high steam pressure in the heating circuit which ranges between 60 to 80 atmospheres so that the small heating surface of the tube 50 (Fig. 5) in connection with the tank or auxiliary boiler comprising the members 53,

54 which is of light weight is adapted to serve its intended purpose and which obviates the necessity of employing a large and cumbersome heat absorbing medium.

2. No skilled attendance is required, the device being always operative, as long as the oven is being heated.

What I claim is:-

1. A steam heating system for baking ovens comprising in combination, a tubular boiler, heating tubes, tubular connections between said boiler and the heating tubes to form a closed pressure proof heating circuit, a separator for the water and steam, and. the water tubes of said boiler having the ends thereof interconnected with said separator for the water and steam mixture, a common collecting tube, said heating tubes being connected thereto, and one of said tubular connections forming the steam supply pipe communicating with one end of said collecting tube, and the other of said tubular connections forming the condensate discharge pipe communicating with the other end of said collecting tube.

2. In a steam heating system for baking ovens comprising in combination, a tubular boiler, heating tubes, tubular connections between said boiler and the heating tubes, a separator for the water and steam mixture interposed in the circuit of the tubular boiler, said connected elements forming a closed pressure proof heating circuit, saidconnections between the heating tubes and the tubular boiler comprising a steam pipe leading from the separator, a common collecting tube communicating with one end of said steam pipe and with the heating tubes, and a condensate return pipe communicating with and leading from the other end of the collecting tube back to the boiler.

3. A steam heating system for baking ovens as claimed in claim 2, comprising an auxiliary boiler interposed in the heating circuit and heated by steam from the heating circuit of the baking oven, said auxiliary boiler having an inlet connection for the supply of water to said auxiliary boiler,

and a steam outlet connection between the boiler 751 Cir and the baking space of the oven, said auxiliary boiler serving to generate steam of low pressure which is blown at intervals into the baking space of the oven.

4. A steam heating system for baking ovens as claimed in claim 2, comprising an auxiliary tubular boiler having an inlet connection communicating with the steam pipe leading from the separator, and an outlet connection communicating with the condensate return pipe,-said boiler comprising a tank heating body, a pipe coil enclosed within the wall of said tank and connected to said inlet and outlet connections, a separate inlet connection for supplying water to the heated surfaces of the boiler, and a steam outlet connection between the boiler and the baking space of the oven, said auxiliary boiler serving to generate steam of low pressure which is blown at intervals into the baking space of the oven.

WILHELM PFEIF'FER. 

